1. Field of the Invention
This invention relates to storage tanks suitable for storing volatile liquids, such as volatile hydrocarbon liquids, and in particular to floating roof tanks and apparatus for sealing the circumferential space between the floating roof and the tank wall.
2. Description of the Prior Art
The use of floating roof tanks for the storage of volatile liquids, such as crude oil, petroleum products and the like, has been widely accepted due to the reduced vapor emissions and improved safety features of floating roof tanks as compared to fixed roof tanks. Floating roof tanks typically have a sealing element disposed in the annular space between the floating roof and the tank wall in order to close this annular space while permitting normal roof movement due to filling and emptying of the tank as well as diurnal expansion and contraction of the stored liquid. The sealing element also serves to keep the floating roof centered in the tank.
The sealing elements currently employed on floating roof tanks include toroidal sealing elements and shoe-type sealing elements, each of which can be used alone or in combination with a secondary seal, such as a wiper sealing element. While these prior art sealing elements are relatively effective in reducing the vapor emissions from floating roof tanks, the very strict requirements of recent governmental regulations and the increasing value of volatile liquids, such as gasoline, have combined to render objectionable even the relatively small vapor emissions from these tanks. Thus a need exists for an improved apparatus for sealing floating roof tanks.
Accordingly, a primary object of this invention is to provide an improved sealing apparatus for floating roof tanks.
Another object of this invention is to provide a simple and effective apparatus for reducing vapor emissions from floating roof tanks.
Yet another object of this invention is to provide an improved sealing apparatus which can be easily assembled from readily available components.
Still other objects, advantages and features of this invention will become apparent to those skilled in the art from the following description when taken in conjunction with the accompanying drawings.